March 2009 - Boost - lists.preview.boost.org

is_virtual_base_of ?
by Robert Ramey 13 Mar '09

13 Mar '09

Is there an implementation of the type trait is_virtual_base_of<D, B> anywhere? If not is there a way to make such a thing? Robert Ramey

7 17

Preview 4 of the Generic Geometry Library (ggl)
by Barend Gehrels 13 Mar '09

13 Mar '09

Dear list, It is a pleasure for us to present the fourth preview of the Generic Geometry Library. This time we've added the library to the SVN repository at boost, https://svn.boost.org/svn/boost/sandbox/ggl To store the library under a proper name, "ggl" is used, which stands for Generic Geometry Library. Before this we called it just Geometry Library, but we think Generic is appropriate from this version on. The first three previews were sent to this list in January, March and October 2008. Since then everything has been revised and reworked again, based on comments from the list. Thanks for all your comments! Concepts are now applied for all geometries. Algorithms now take any geometry fulfilling the concepts, and automatically take the right version of the underlying implementation. Ranges are now used instead of .begin()/end(). Tag dispatching is used instead of SFINAE. Transformations: previously these were just explained as an example, now transformations are included in the library, either to go from one coordinate system to another (for example from spherical to cartesian3D) or to translate/rotate/scale/map points from one Cartesian system to another, or otherwise. Map projections: included is an extensive addition with nearly 100 map projections. Those are not programmed by ourselves but automatically converted from C (PROJ4) into a our template-based approach, fitting with the geometry library, especially in the transformations explained above. License-wise this is possible. We're not sure about if this would fit in the Boost Library Collection, if there is interest in it, or that it might be "too much" for it, so we would be glad to hear your opinions. For more change descriptions, see the page on status and preview from the documentation (link below). The Generic Geometry Library is accessible from Boost SVN, mentioned above, or can be downloaded as well from http://geometrylibrary.geodan.nl Especially the examples, such as the custom point example and custom line string example show nicely how the library handles custom geometries and how they can be used inside the generic algorithms. We welcome any type of comment, opinion, cooperation, merge or join. Barend Gehrels, Amsterdam Bruno Lalande, Paris

3 11

GSoC 2009 Status
by troy d. straszheim 13 Mar '09

13 Mar '09

All- Our application to be a mentoring organization for the fourth year is in, I'm idling on the gsoc channel and watching things develop. We'll know soon if boost is accepted again this year, and at that time we'll be able to start getting our mentors into the system. Meanwhile there is a (currently empty) wiki page for project ideas: https://svn.boost.org/trac/boost/wiki/soc2009 Please feel free to post your gsoc ideas there. I believe there will be a stage soon where students will see that we are a potential mentoring organization and will peruse this list, looking for things that interest them... so have at it. -t

1 0

[accumulator] reset?
by Neal Becker 13 Mar '09

13 Mar '09

I don't suppose accumulators implement a reset?

2 1

[math] calculate derivative automatically.
by Dongfei Yin 13 Mar '09

13 Mar '09

> I personally signaled my interest for something much more general than > only derivatives. But as Dongfei's goal seems to be focused in that > direction Hi Bruno, Actually, I do interesting in simplifying, not only derivative. If you have good idea, we can work it out together if you don't mind. Some times, a expression is simply for computer but not for human. compromising is always needed, and it is hard to make a choice. But as you said, just for compile-time integral value, things become easier. Like the volume of hypersphere, when N = 2, after simplified, computation will be reduced a lot. Dongfei.

2 1

Boost.Asio asio::basic_socket_acceptor
by Joshua Pedrick 13 Mar '09

13 Mar '09

I'm trying to write an application that can simply switch between using local stream sockets and tcp stream sockets. I successfully implemented this behavior with BSD sockets in Linux, but it seems the class hierarchy in boost::asio makes this behavior awkward, since asio::basic_socket_acceptor template requires a protocol type, but there is so base class for protocols. I'm wondering if there is a reason for this or if it could possibly be changed? Basically, I have a client/server library for distributed processing, which in some cases, I wish to run using local sockets and other times run using TCP sockets. I was hoping Boost Asio could make the solution a little more elegant/clean, but at the moment I can't find an elegant manner to do this. I'd be glad to do all the work for this, provided some guidance, but I basically don't want to build my application on a custom version of boost::asio, which won't improve with the main version. So if this can't be changed, I just won't use asio, but if it can, I'll go ahead and take the time to implement the changes

2 1

To create a boost thread
by Filip Klasson 13 Mar '09

13 Mar '09

Hi, I have problems creating a thread. This is an example i found: #include <boost/thread/thread.hpp> #include <iostream> void hello() { std::cout << "Hello world, I'm a thread!" << std::endl; } int main(int argc, char* argv[]) { boost::thread thrd(&hello); thrd.join(); return 0; } What if i want to create a thread outside of main (in a class) like this: "myClass.h" class MyClass { public: hello(); myFunction(); }; "myClass.cpp" MyClass::hello() { std::cout << "Hello world, I'm a thread!" << std::endl; } MyClass::myFunction() { boost::thread thrd(&hello); thrd.join(); } This does not work and i get the compile error: '&' : illegal operation on bound member function expression

4 4

Re: [boost] [Fwd: Re: Google SOC Mentors?]
by Niall Douglas 12 Mar '09

12 Mar '09

On 12 Mar 2009 at 15:41, troy d. straszheim wrote: > >> Do have any interest in teaming up on this? > > > > Umm sure ... I can't find the message below in the Boost mailing list > > archives, so I'm unsure as to context. > > > > But if it's to mentor Google SoC then yes please, though do note I am > > extremely time pressed until the start of June after which I'll be > > finally free of academia. > > > > i.e. please do put my name forward. > > > > No worries. Whatever happens will be done on the mailing lists and > IRC, so you can join in at any point. Just to let everyone know, I have subscribed to boost(a)lists.boost.org and will remain until the Google SoC process is over. This is a very high volume list - this is why I normally lurk around Boost.Python only - so I won't be staying for much past the SoC process. I am *extremely* time pressed before the start of June and will neither be able to access IRC nor my own email (thank you very much university firewall!). However start of June onwards I'll be finally free and working from home for the next few years. Looking forward to hearing from you all, Niall

1 0

[mpi] Boost.MPI + GCC 4.3 + MPICH2 (1.0.3) Issue on Gentoo
by Dean Michael Berris 12 Mar '09

12 Mar '09

Hi Guys, Anybody been successful with combining Boost.MPI and MPICH2 before? I keep getting this link-time error about 'now' couldn't be found. The command I get from Boost.Build + Boost.Jam is the following (stripped of Friendster-specific names/symbols): "g++-4.3.3" -L"/usr/lib64" -o "output" -Wl,--start-group "main.o" "boost_1_38_0/bin.v2/libs/mpi/build/gcc-4.3.3/debug/link-static/optimization-speed/threading-multi/libboost_mpi-gcc43-mt-d-1_38.a" "boost_1_38_0/bin.v2/libs/serialization/build/gcc-4.3.3/debug/link-static/optimization-speed/threading-multi/libboost_serialization-gcc43-mt-d-1_38.a" -Wl,-Bstatic -Wl,-Bdynamic -lmpich -lpthread -lrt -lrt -Wl,--end-group -g -pthread -O2 -Wl,-rpath -Wl,-z,now -Wl,/usr/lib64 -march=opteron -pipe The auto-configuration worked for MPI: ===============MPI Auto-configuration=============== Found MPICH wrapper compiler: mpicc MPI compilation flags: -march=opteron -O2 -pipe -Wl,-z,now -I/usr/include -L/usr/lib64 -Wl,-rpath -Wl,/usr/lib64 -lmpich -lpthread -lrt MPI link flags: -march=opteron -O2 -pipe -Wl,-z,now -I/usr/include -L/usr/lib64 -Wl,-rpath -Wl,/usr/lib64 -lmpich -lpthread -lrt MPI build features: <include>/usr/include <library-path>/usr/lib64 <find-shared-library>mpich <find-shared-library>pthread <find-shared-library>rt <cxxflags>-march=opteron <cxxflags>-O2 <cxxflags>-pipe <cxxflags>-Wl,-z,now <cxxflags>-Wl,-rpath <cxxflags>-Wl,/usr/lib64 <include>/usr/include <library-path>/usr/lib64 <find-shared-library>mpich <find-shared-library>pthread <find-shared-library>rt <linkflags>-march=opteron <linkflags>-O2 <linkflags>-pipe <linkflags>-Wl,-z,now <linkflags>-Wl,-rpath <linkflags>-Wl,/usr/lib64 MPI launcher: mpirun -np ==================================================== In my Jamfile I have something like the following: exe output : main.cpp : <source>/boost//mpi <library>/mpi//mpi ; Am I missing anything obvious? TIA -- Dean Michael Berris | Software Engineer, Friendster, Inc. blog.cplusplus-soup.com | twitter.com/mikhailberis | linkedin.com/in/mikhailberis | profiles.friendster.com/mikhailberis | deanberris.com

2 3

[iostreams][repost] How can code conversion failure be detected
by Eric MALENFANT 12 Mar '09

12 Mar '09

Hi, I posted what's quoted below a while ago on the boost devel mailing list, but received no replies. (Naïvely?) assuming that this lack of feedback was caused by the excessive length of the post, let me try to summarize it: For the purpose of this example, assume the existence of always_fail_cvt, a codecvt facet which always returns "fail" namespace bio = boost::iostreams; std::wofstream fs("whatever"); fs.imbue(std::locale(fs.getloc(), new always_fail_cvt)); bio::filtering_wostream s(fs); s << L"Hello"; std::cout << std::boolalpha << s.good() << '\n'; // 1 s.flush(); // 2 std::cout << s.good() << '\n'; // 3 "s" being buffered, it is not surprising that line //1 outputs "true" (nothing failed yet, "Hello" is in the buffer) By stepping in the code, I see that line //2 tries to empty the buffer by calling sputn() on the underlying wofstream's filebuf, which fails because code conversion fails. I thus find it surprising that line //3 also ouputs "true" I'm also surprised that line //2 does not cause flush() to be called on the wofstream, or pubsync() on its filebuf Is this a bug or am I wrong in assuming that 1) The codecvt error occuring during flush() should cause the failbit to be set on the filtering_stream 2) flush()-ing a filtering_ostream wrapping an std::ostream should flush() the std::ostream ? Thanks, Éric Malenfant Original post follows: By default, filtering_streams do buffering. This means that what is written to them does not necessarily reach the underliyng Filters and Device immediately. It is thus my understanding that, in order to be sure that all data was written, one should somehow flush the buffered data, and then check the stream state before closing it. As a first attempt, I tried flush(), but it does not seem to do what I expected, as it is pretty lax in the failures that it tolerates. Looking at the docs, I then found what seemed to be what I was looking for: strict_sync(), whose documentation states that "A return value of true guarantees that all buffered data has been successfully forwarded.". Moreover, the FAQ entry "Can I swap Filters or Devices in the middle of a sequence of i/o operations?" seems to confirm this, as it says: "First call strict_sync. If it returns true, you can safely call set_auto_close(false) and pop one or more components without closing the stream. This applies to instances of filtering_stream, filtering_streambuf and chain." But again, this did not work: strict_sync() returns true altough buffered data remains. Consider this contrived example: // A codecvt facet that always fails class always_fail_cvt : public std::codecvt<wchar_t,char,mbstate_t> { protected: virtual result do_unshift(state_type&, char*, char*, char*&) const { return std::codecvt_base::error; } virtual int do_encoding() const throw() { return -1; } virtual bool do_always_noconv() const throw() { return false; } virtual int do_length(const state_type&, const char*, const char*, size_t max) const { return max; } virtual int do_max_length() const throw() { return 4; } virtual result do_out(state_type&, const intern_type*, const intern_type*, const intern_type*&, char* to, char*, char*&) const { return std::codecvt_base::error; } virtual result do_in(state_type&, const char*, const char*, const char*&, intern_type*, intern_type*, intern_type*&) const { return std::codecvt_base::error; } }; int main(int argc, char* argv[]) { namespace bio = boost::iostreams; std::wofstream fs("whatever"); fs.imbue(std::locale(fs.getloc(), new always_fail_cvt)); bio::filtering_wostream s(fs); s << L"Hello"; std::cout << std::boolalpha << s.good() << '\n'; // 1 s.flush(); std::cout << s.good() << '\n'; // 2 return 0; } Running this (on Windows with MSVC 7.1) produces true true The first "true", is not surprising, as the characters are buffered and code conversion has not taken place yet, but the second is. Considering the presence of strict_sync(), I assumed that the laxism of flush() is intentional, to allow stateful filters to retain buffered data, maybe. However, replacing the "s.flush();" line in the above program with "std::cout << s.strict_sync() << '\n';" does not seem to improve things. Although a conversion failure occured and data remains buffered, strict_sync() returns true, and the stream's state is still good(). So, to sum up: 1) If my understanding of the semantics of strict_sync() is correct, it seems that indirect_streambuf::strict_sync() should verify that the buffer is empty after the call to sync_impl(), and fail if it is not the case. Something like this maybe: template<typename T, typename Tr, typename Alloc, typename Mode> bool indirect_streambuf<T, Tr, Alloc, Mode>::strict_sync() { try { // sync() is no-throw. sync_impl(); return obj().flush(next_) && ((pptr() - pbase()) != 0); // Added this --^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ } catch (...) { return false; } } 2) Is it "correct" that filtering_stream::flush() does not completely flush without reporting an error? 3) Does this come from an incompatibility between Boost.IOStreams idea of error-reporting (throwing exceptions) and that of the std streambufs (returning EOF, mainly)? In particular, Boost.IOStreams writes in a wrapped std::streambuf by using sputn(), which, AFAI(don't)U, does not have a clear error reporting strategy. IOWs, should write_device_impl<streambuf_tag>::write() be modified like this: template<typename T> static std::streamsize write (T& t, const typename char_type_of<T>::type* s, std::streamsize n) // { return t.sputn(s, n); } { std::streamsize count = t.sputn(s, n); if (count == n){ return count; } // If all characters could not be written, check if it is because of an error or only because of blocking if (T::traits_type::eq_int_type(t.sputc(s[count]), T::traits_type::eof())){ throw std::ios_base::failure("write error"); } else{ return count + 1; } } so that errors occuring during a write on std::streams and streambufs are reported by an exception? -- Éric Malenfant If it ain't broke, you're not trying hard enough. - Seen on the Google testing blog home page

1 0